Flexible shared mesh protection services for intelligent TDM-based optical transport networks

ABSTRACT

A system includes one or more active/working circuit groups to transfer information through a protection domain, the protection domain defined by a plurality of network devices and a plurality of links connecting the network devices between a start point and an end point; and a protection circuit group through the protection domain, the protection circuit group being disjoint from the one or more active/working circuit groups to provide shared protection for the one or more active/working circuit groups, where the protection circuit group is comprised of an individual protection circuit and where a capacity of the protection circuit group is dynamically adjusted based on a capacity of the one or more active/working circuit groups.

BACKGROUND INFORMATION

Service providers are migrating their Layer 0 (wavelength-divisionmultiplexing management or WDM) and Layer 1 (time-division multiplexingor TDM) core networks into integrated intelligent optical transportnetworks (IOTNs). In some cases, previous network management system(NMS)-based procedures are being phased out by the deployment of anintelligent control plane in the IOTNs. IOTNs may support mesh topologyto achieve better resource utilization and may support a distributedcontrol plane to fully automate networking functions, such as networktopology discovery, network resource discovery, end-to-end pathcalculation, end-to-end path provisioning and activation, and protection& restoration (P&R). The IOTN control plane and mesh topology togetherhave provided opportunities for service providers to develop advancedoptical transport network (OTN) services that are better tailored to thebusiness needs of wholesale and enterprise customers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary network in which systems and methodsdescribed herein may be implemented;

FIG. 2 depicts an exemplary network management system device for theexemplary network illustrated in FIG. 1;

FIG. 3A depicts an exemplary network device configured to communicatevia the exemplary network illustrated in FIG. 1;

FIG. 3B is a diagram of a management system of the exemplary networkdevice illustrated in FIG. 3A;

FIG. 3C is a diagram of a call processing system of the exemplarynetwork device illustrated in FIG. 3A;

FIG. 4A is a diagram of an exemplary 1+1 mesh protection service shownwith five protection domains;

FIG. 4B is a diagram of an exemplary 1+1 mesh protection service shownwith a single protection domain;

FIG. 5A is a diagram of an exemplary flexible shared mesh protectionservice shown in normal operation over an exemplary network;

FIG. 5B is a diagram of an exemplary flexible shared mesh protectionservice shown compensating for a network failure over an exemplarynetwork;

FIG. 5C is a flow diagram of an exemplary process flow for setting up aflexible shared mesh protection service mechanism;

FIGS. 6A-B are exemplary data tables for protection circuit groups;

FIGS. 7A-B are exemplary data tables for active circuit groups;

FIGS. 8-15 are flow diagrams illustrating exemplary portions of anexemplary flexible shared mesh protection service according toimplementations described herein;

FIG. 16 is a diagram of an exemplary network showing how service levelparameters can be used to instruct all P-domains in a network to triggerthe FSMPS mechanism; and

FIG. 17 is a diagram of an exemplary network implementing FSMPS.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements. Also, the following detailed description does notlimit the invention.

Automated data plane routing and signaling functions by networkequipment may permit a network to direct a flow of information streamsor traffic along a particular path (e.g., a label switched path) acrossthe network. An “information stream” may include any type or form ofdata stream, such as packet or non-packet data streams. A user mayspecify the start point, end point, and bandwidth (BW) required, and arouting agent may allocate the path through the network, may provisionthe traffic path, may set up cross-connects, and may allocate bandwidthfrom the paths for a user-requested service. The actual path that thetraffic may take through the network may not be specified by the user.

As defined by international standards bodies, a control planearchitecture framework may be defined by three network interfaces: anexternal-network network interface (E-NNI), an internal-network networkinterface (I-NNI), and/or a User Network Interface (UNI). An E-NNI mayprovide a demarcation point that supports cross-domain connectionprovisioning (e.g., intra-carrier/inter-domain (trusted) connectionsand/or inter-carrier (un-trusted) connections), and may providesignaling with limited routing information exchanges. An I-NNI mayprovide an intra-domain (trusted) node-to-node interface that supportscontrol plane functions, and may provide intra-domain signaling and/orrouting functions. A UNI may provide a demarcation point between usersand a network, may be an un-trusted interface, and may provide signalingcapabilities to the users.

An intelligent control plane may support auto-discovery and/orself-inventory of network resources, topology, connection map, etc. Anintelligent control plane may also support end-to-end path calculations,dynamic end-to-end path setup and teardowns in a single-step and/orsingle-ended fashion, and/or a variety of protection and/or restorationschemes. An intelligent control plane may provide several benefits,including improved network efficiency, enhanced network resiliency, newrevenue opportunities, etc.

Systems and methods disclosed herein may provide a mechanism for andclass of flexible shared mesh protection (FSMP) services. The FSMPmechanism may use the dynamic provisioning capability of an opticalcontrol plane and SONET/SDH adaptive-rate port technologies. The FSMPmechanism can transform shared mesh technology into a service-readytechnology platform, upon which advanced shared mesh protection servicescan be offered. The flexible shared mesh protection service (FSMPS) mayuse a minimal amount of protection capacity to support circuitrestorations; thus FSMPS may provide a cost savings to serviceproviders.

The systems and methods described herein may be applied to variouscontrol plane interfaces (e.g., an I-NNI or E-NNI) for TDM-based OTNs,and thus, may provide a mechanism to manage shared protection bandwidthon core networking layers (e.g., “Layer 1” (TDM)). The systems andmethods may also permit dynamic adjustment of shared protection capacityby the control plane.

FIG. 1 depicts an exemplary network 100 in which systems and methodsdescribed herein may be implemented. Network 100 may include multipleI-NNI domains 110-1, 110-2 and 110-3 (collectively referred to as either“I-NNI domains 110 or control plane (CP) domains 110”), multiple E-NNIs120 interconnecting the CP domains 110, and one or more networkmanagement system/operations support system (NMS/OSS) 130. Each of CPdomains 110 may include multiple I-NNI links 140 and multiple networkdevices 150. Additionally, clients 160 may be linked to various networkdevices 150 via UNI links 170. In FIG. 1, three CP domains 110, twoE-NNI interfaces 120, two NMS/OSS 130, eleven I-NNI links 140, tennetwork devices 150, four clients 160, and four UNI links 170 have beenillustrated for simplicity. In practice, there may be more or fewerdomains, E-NNI links, control planes, I-NNI links, network devices,clients, and/or UNI links.

CP domains 110 may include local area networks (LANs), wide areanetworks (WANs), metropolitan area networks (MANs), telephone networks(e.g., the Public Switched Telephone Network (PSTN)), intranets, or acombination of networks. In one implementation, for example, CP domains110 may include Next Generation Transfer Networks (NG-TNs), such as NextGeneration Optical Transfer Networks (NG-OTNs). In certainimplementations, clients 160, network devices 150, and/or NMS/OSS 130may interconnect and/or connect to CP domains 110 via wired and/orwireless connections.

E-NNI 120 may include physical media that interconnects CP domains 110.In one implementation, E-NNI 120 may support multiple E-NNI linkscapable of supporting cross-domain connection provisioning (e.g.,intra-carrier/inter-domain (trusted) connections and/or inter-carrier(un-trusted) connections), and/or capable of providing cross-domainsignaling and routing. E-NNI 120 may include links that physicallyconnect to ports (e.g., input ports or output ports) provided on networkdevices 150, and may be configured by provisioning software provided inmanagement systems of network devices 150.

NMS/OSS 130 may include a device (e.g., a server), or group of devices,capable of supporting one or more control planes in an IOTN thatprovides design and/or routing of end-to-end circuits (or circuitswithin a domain) and dynamic provisioning of protection for thosecircuits. Additional details of NMS/OSS 130 are provided below inconnection with FIG. 2.

I-NNI links 140 may include a physical media that interconnects adjacentnetwork devices 150. For example, I-NNI links 140 may provide a paththat permits communication among network devices 150. In oneimplementation, for example, network links 140 may support I-NNIscapable of providing intra-domain (trusted) node-to-node interfaces thatsupport control plane functions, and/or capable of providingintra-domain signaling and/or routing functions. Similar to E-NNI linksdescribed above, I-NNI links 140 may physically connect to ports (e.g.,input ports or output ports) provided on network devices 150, and may beconfigured by provisioning software provided in management systems ofnetwork devices 150.

Each network device 150 may include a device, such as a multiplexer, arouter (e.g., a Layer 3 router), a switch (e.g., a Layer 2 switch), anoptical cross connect (OCX), a hub, a bridge, a reconfigurable opticaladd and drop multiplexer (ROADM), a dense wavelength divisionmultiplexer (DWDM) (e.g., a Layer 0 DWDM), or another type ofcomputation or communication device capable of running on any layer.Additional details of network devices 150 are provided below inconnection with FIGS. 3A-3C.

Clients 160 may include client entities. An entity may be defined as adevice, such as a personal computer, a telephone (e.g., wired, wireless,SIP, etc.), a personal digital assistant (PDA), a television, a laptop,or another type of computation or communication device, a thread orprocess running on one of these devices, and/or an object executable byone of these devices. Clients 160 may connect to network devices 150,may function as endpoints for network 100, and/or may use servicesprovided by network 100. Each client 160 may be connected to a networkdevice 150 via a UNI link 170.

In an exemplary implementation, network 100 may be an IOTN including anintelligent control plane (e.g., supported by NMS/OSS 130). The networktopology can be a mesh that supports at least two-degree route diversitybetween a pair of end-points. Diversity can be measured, for example, interms of shared risk link group (SRLG) diversity, where K-degreediversity means there exists K fully SRLG diverse routes availablebetween the end-points of interest. Network 100 may be operated with anoptical-TDM control plane. All control-plane-managed TDM ports maysupport an adaptive-rate (or auto-concatenation) feature, which allows aprotection circuit to automatically adjust its payload structures to thestructure of restored customer circuits. A protection circuit may serveas a backup for one or more customer circuits in the event of a failurewithin the network. The control plane may provide explicit routesupport. For example, the control plane routing can route a customercircuit according to an operator-selected route. The control plane maysupport shared risk link group (SRLG) diversity. SRLG values can beassigned to essentially any network resources (e.g., fiber cables,central offices, network switches/nodes, conduits, WDM amplifier chains,circuit packs, etc.) through which the control plane provisions customercircuits. Any fault on these network resources can cause interruptionsto customer services. The control plane can be capable of provisioningcircuits/services according to customer SRLG diversity requirements. Thecontrol plane may also support SRLG retrieval for established customerand protection circuits.

Although FIG. 1 shows exemplary components of network 100, in otherimplementations, network 100 may contain fewer or additional componentsthat may provide a FSMP mechanism for control plane enabled networksthat perform end-to-end path routing. In still other implementations,one or more components of network 100 may perform the tasks performed byother components of network 100. The systems and methods describedherein may be used for any device that supports control plane enablednetworks using TDM-based OTN routing protocols to perform circuit pathrouting.

FIG. 2 is an exemplary diagram of a device which may correspond toNMS/OSS 130. As shown, NMS/OSS 130 may include a bus 210, a processor220, a main memory 230, a read only memory (ROM) 240, a storage device250, and a communication interface 260. Bus 210 may include a path thatpermits communication among the components of NMS/OSS 130.

Processor 220 may include a processor, microprocessor, or processinglogic that may interpret and execute instructions. Main memory 230 mayinclude a random access memory (RAM) or another type of dynamic storagedevice that may store information and instructions for execution byprocessor 220. ROM 240 may include a ROM device or another type ofstatic storage device that may store static information and instructionsfor use by processor 220. Storage device 250 may include a magneticand/or optical recording medium and its corresponding drive.

Communication interface 260 may include any transceiver-like mechanismthat enables NMS/OSS 130 to communicate with network devices and/orsystems. For example, communication interface 260 may include mechanismsfor communicating with network devices and/or systems via a network,such as network 100.

As will be described in detail below, NMS/OSS 130 may perform certainrouting operations. NMS/OSS 130 may perform these operations in responseto processor 220 executing software instructions contained in acomputer-readable medium, such as memory 230. A computer-readable mediummay be defined as a physical or logical memory device.

The software execution may be directly or indirectly triggered bynetwork events and/or network operator inputs. The software instructionsmay be read into memory 230 from another computer-readable medium, suchas data storage device 250, or from another device via communicationinterface 260. The software instructions contained in memory 230 maycause processor 220 to perform processes that will be described later.Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, implementations described herein are not limited to anyspecific combination of hardware circuitry and software.

Although FIG. 2 shows exemplary components of NMS/OSS 130, in otherimplementations, NMS/OSS 130 may contain fewer or additional componentsthat may provide a FSMP mechanism for control plane enabled networks. Instill other implementations, one or more components of NMS/OSS 130 mayperform the tasks performed by other components of NMS/OSS 130.

FIG. 3A is an exemplary diagram of a device that may correspond to oneof network devices 150. The device may include input ports 310, aswitching mechanism 320, output ports 330, a management system 340, acall processing system 350, a routing system 360, and/or a signalingsystem 370. Generally, input ports 310 may be the point of attachmentfor a physical link (not shown) and may be the point of entry forincoming traffic. Switching mechanism 320 may connect input ports 310with output ports 330. Output ports 330 may store traffic and mayschedule traffic for service on an output link (not shown). Managementsystem 340 may enable communication between NMS/OSS 140 and componentsof network device 130. Call processing system 350 may manage processingand circuit allocation decisions for sharing protection bandwidth.Routing system 360 may participate in routing protocols. Signalingsystem 370 may activate paths between particular nodes.

Input ports 310 may carry out service adaptation, datalink layerencapsulation and decapsulation. Input ports 310 may look up adestination address of incoming traffic in a forwarding table todetermine its destination port (i.e., route lookup). In order to providequality of service (QoS) guarantees, input ports 310 may classifytraffic into predefined service classes. Input ports 310 may run opticallayer framing protocols, datalink-level protocols, or network-levelprotocols.

Switching mechanism 320 may be implemented using many differenttechniques. For example, switching mechanism 320 may include busses,crossbars, and/or shared memories. The simplest switching mechanism 320may be a bus that may link input ports 310 and output ports 330. Acrossbar may provide multiple simultaneous data paths through switchingmechanism 320. In a shared-memory switching mechanism 320, incomingtraffic may be stored in a shared memory and pointers to traffic may beswitched.

Output ports 330 may store traffic before the traffic is transmitted onan output link (not shown). Output ports 330 may include schedulingalgorithms that support priorities and guarantees. Output ports 330 maysupport datalink layer encapsulation and decapsulation, and/or a varietyof higher-level protocols.

Management system 340 may connect with input ports 310, switchingmechanism 320, output ports 330, call processing system 350, routingsystem 360, and signaling system 370. Management system 340 maycommunicate with NMS/OSS 130 and may perform provisioning,configuration, reporting, and/or maintenance functions for networkdevice 150. Additional details of management system 340 are providedbelow in connection with FIG. 3B.

Call processing system 350 may construct a protection circuit group(PCG) database, an active/working circuit groups (ACG) database, computea forwarding table(s), implement routing protocols, and/or run softwareto configure and/or manage network device 150. Call processing system350 may include a processor, the PCG database, and the ACG database,routing tables, etc.

Routing system 360 may handle any traffic whose destination address maynot be found in the forwarding table. Routing system 360 may include arouting engine or protocol processor, routing tables, etc. Signalingsystem 370 may activate paths between particular nodes and/or mayimplement signaling protocols for network device 150.

Although FIG. 3A shows exemplary components of network devices 150, inother implementations, network devices 150 may contain fewer oradditional components than depicted in FIG. 3A. For example, in oneimplementation, one or more components of network devices 150 depictedin FIG. 3A may perform the tasks performed by other components ofnetwork devices 130. Although FIG. 3A shows network devices 150 asincluding routing system 360 (i.e., a distributed routing system for anetwork), in other implementations, a centralized routing system may beprovided for a network and routing system 360 may be omitted fromnetwork devices 150.

FIG. 3B is an exemplary diagram of a device that may correspond tomanagement system 340 of network device 150. As shown, management system340 may include a bus 341, a processor 342, a memory 343, an interface344 for input ports 310, an interface 345 for output ports 330, and acommunication interface 346. Bus 341 may include a path that permitscommunication among the components of management system 340.

Processor 342 may include a processor, microprocessor, or processinglogic that may interpret and execute instructions, such as instructionsfrom an external source or from call processing system 350. Memory 343may include a random access memory (RAM) or another type of dynamicstorage device that may store information and instructions for executionby processor 342. Interfaces 344 and 345 may include a mechanism thatpermits interconnection with input ports 310 and output ports 330,respectively. Communication interface 346 may include anytransceiver-like mechanism that enables management system 340 tocommunicate with other devices and/or systems, either internal orexternal. For example, communication interface 346 may includemechanisms for communicating with NMS/OSS 130 or components of networkdevice 150, such as switching mechanism 320 and call processing system350.

As will be described in detail below, management system 340 may performcertain operations to implement flexible shared mesh protectionservices. Management system 340 may perform these operations in responseto processor 342 executing software instructions contained in acomputer-readable medium, such as memory 343.

The software instructions may be read into memory 343 from anothercomputer-readable medium or from another device via communicationinterface 346. The software instructions contained in memory 343 maycause processor 342 to perform processes that will be described later.Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, implementations described herein are not limited to anyspecific combination of hardware circuitry and software.

Although FIG. 3B shows exemplary components of management system 340, inother implementations, management system 340 may contain fewer oradditional components that may provide a FSMP mechanism for controlplane enabled networks. In still other implementations, one or morecomponents of management system 340 may perform the tasks performed byother components of management system 340.

FIG. 3C is an exemplary diagram of a device that may correspond to callprocessing system 350. As shown, Call Processing system 350 may includea bus 351, a processor 352, a protection circuit group (PCG) database353, an active circuit group (ACG) database 354, a memory 355, and acommunication interface 356.

Bus 351 may include a path that permits communication among thecomponents of routing system 350. Processor 352 may include a processor,microprocessor, or processing logic that may interpret and executeinstructions. PCG database 353 may include a storage device that maystore information and instructions for execution by processor 352. Forexample, PCG database 353 may store one or more PCG tables (PCGT) and orone or more PCG protection table (PPT). Similarly, ACG database 354 mayinclude a storage device that may store information and instructions forexecution by processor 352. For example ACG, database may store one ormore ACG table. Exemplary PCGT, PPT and ACG tables and their uses arediscussed in more detail with respect to FIGS. 6A, 6B, 7A and 7B. Memory355 may include a RAM, ROM, another type of storage device that maystore information and instructions for execution by processor 352.Memory 355 may optionally include forwarding tables, routing tables, orprotocol information. Communications interface 356 may include amechanism that permits interconnection with adjacent network devices150.

As will be described in detail below, call processing system 350 mayperform certain operations to implement flexible shared mesh protectionservices. Call processing system 350 may perform these operations inresponse to processor 352 executing software instructions contained in acomputer-readable medium, such as PCG database 353 and/or ACG database354.

Link status information and/or software instructions may be read intoPCG database 353 and/or ACG database 354 from another computer-readablemedium, such as memory 355, or from another device. The information andinstructions contained in PCG database 353 and/or ACG database 354 maycause processor 352 to perform processes that will be described later.Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, implementations described herein are not limited to anyspecific combination of hardware circuitry and software.

Although FIG. 3C shows exemplary components of call processing system350, in other implementations, call processing system 350 may containfewer or additional components that may provide a FSMP mechanism forcontrol plane enabled networks that perform end-to-end path routing. Instill other implementations, one or more components of call processingsystem 350 may perform the tasks performed by other components of callprocessing system 350.

An IOTN may consist of multiple CP domains interconnected with E-NNIs.For example, I-NNI domains 110-1, 110-2 and 110-3 of FIG. 1 may each bea separate CP domain. In certain implementation, each CP domain can bedefined to coincide with a vendor platform domain or a networkprovider's administrative domain. There may be multiple ways toprovision an end-to-end circuit with certain protection and restoration(P&R) requirements. One way is to implement the desired P&R schemewithin an individual domain (e.g., each of I-NNI domains 110-1, 110-2 an110-3) and over each E-NNI (e.g., E-NNI 120), so that implementations onthe I-NNI domains and E-NNIs are totally independent from each other.

FIG. 4A shows an example of a system 400 including a 1+1 protectedend-to-end circuit provisioned by the CP using five 1+1 protectedsegments over Domains A, B, and C and two E-NNIs. Each segmentrepresents fully-diverse working and protection paths within the localdomain or E-NNI. The end-to-end circuit is 1+1 protected segmentally,but from end user point of view the circuit is 1+1 protected end-to-end.In this approach, each CP domain is defined as a protection domain(P-domain). Any end-to-end P&R requirement can be implemented bymultiple P-domains, as exemplified in FIG. 4A for 1+1 protection.

Another way to support end-to-end P&R is to treat all CP domains withinan IOTN as one single P-domain, as illustrated in FIG. 4B. FIG. 4B showsan example of a system 450 where the end-to-end working and protectionpaths are calculated as two end-to-end paths which are fully diverse(both link and node) from the source to the destination node. Thisapproach may be called single P-domain approach. There can be many otherapproaches using different ways to combine individual P-domains to meetan end-to-end P&R requirement. Similar to the foregoing 1+1 P&R example,FSMPS circuits as described herein can be implemented using acombination of multiple P-domains or a single P-domain.

When a service request arrives at a source node, the source node mayneed an indication of what P&R is requested for the FSMP service inorder to implement the service in the source node's P-domain. A “ServiceLevel” indicator, discussed in more detail with respect to FIG. 16, mayprovide the necessary indication for each service node.

FIG. 5A is a diagram of an exemplary FSMPS setup shown in normaloperation over an exemplary E-NNI P-domain 500 in one implementation.E-NNI P-domain 500 joins first domain 510 and second domain 520. Firstdomain 510 and second domain 520 may be connected by multiple E-NNIlinks, including E-NNI links 530, 532, and 534. Multiple I-NNI links mayconnect network devices, such as network devices 514 and 516 withindomain 510 and network devices 524 and 526 within domain 520. ThreeSONET client circuits 540, 542, 544 of different types may be connectedbetween network devices 514 and 524. Client circuits 540, 542, 544 shareone protection circuit in E-NNI P-domain 500. Protection circuit 550serves between domains 510 and 520. Domain 510 may select three mutuallydisjointed prototype paths to domain 520 (one for each of circuits 540,542 and 544) which are fully diverse from protection circuits 550, 560,and 570. Client circuits 540, 542, and 544 may form an ACG for E-NNIP-domain 500.

In the example of FIG. 5A, if faults occur within any of E-NNI links 530or 534, circuit restoration using FSMPS may take place within thefaulted domain. The customer circuits along the I-NNI links in domains510 and 520 may not be affected.

FIG. 5B is a diagram of an exemplary FSMPS setup shown compensating fora network failure in E-NNI P-domain 500. More particularly, FIG. 5Bshows E-NNI P-domain 500 with a failure of E-NNI link 534 and circuitrestoration using FSMPS. Customer circuits 542 and 544 have beenswitched from E-NNI link 534 to protection circuit 550 on E-NNI link532. The switch of customer circuits 542 and 544 to E-NNI link 532 maybe temporary. After repairing the failure of E-NNI link 534, customercircuits 542 and 544 may be switched from link 532 back to link 534.

FIG. 5C provides a flow diagram of an exemplary process flow 500 forsetting up a FSMP mechanism. The FSMP mechanism described herein mayinclude two kinds of circuit groups: a protection circuit group (PCG)and one or more active/working circuit groups (ACG). The two types ofcircuit groups may be used within in each P-domain to support the FSMPSservice in each P-domain. A primary protection circuit and all secondaryprotection circuits may belong to the PCG. All client circuits which aresubject to protection may be members of one or more ACGs. A database oftables may be created as the service database to keep track of allprovisioning and protection switching activities within each circuitgroup. The construction of the circuit groups and the formulation of thedatabase tables are further discussed below with respect to FIGS. 6A,6B, 7A and 7B.

Still referring to FIG. 5C, one or more active/working circuit group(ACG) may be configured (block 580). Regarding ACG construction, aservice provider can pre-select multiple preferred, fully-SRLG disjointprototype paths between nodes of interest within a P-domain (such as thetwo fully-SRLG disjoint E-NNI links 530 and 534 between network devices516 to 526 in FIGS. 5A and 5B). The selected prototype paths (Prtp-path)can be mutually SRLG disjoint and best-effort node disjoint. Theseprototype paths can also be fully SRLG and fully node disjoint from theprotection circuits in PCG. Each selected prototype path with associatedSRLG values may define an ACG in the P-domain.

A primary protection circuit group (PCG) may be configured (block 582).Regarding PCG construction, a service provider may build out one initialPCG between two nodes of interest within a P-domain (such as, e.g.,circuit, 532 between network devices 516 to 526 in FIGS. 5A and 5B) witha bandwidth, BW-P, dedicated to protect all circuits provisioned byFSMPS customers within the P-domain. The PCG can be setup using one ofseveral control plane protection schemes, including, for example,unprotected, mesh or SONET/SDH 1+1 protected with full SRLG diversityand full node diversity, mesh 1+1 protected with full SRLG diversity andbest-effort node diversity, mesh 1+1 protected with full SRLG diversityand no node diversity, or a full-time 1+1 protection. PCG bandwidth canbe used to transport select customer traffic when the bandwidth is notused to protect ACG circuits (i.e., BW-P may be used to support extratraffic). Multiple protection circuits may be allowed in the PCG as moreFSMPS customers are added. With multiple PCG protection circuits, eachadditional PCG protection circuit can be co-routed with the primaryprotection circuit (i.e., passing through the same node-sequence as theprimary), but may use diverse SRLG links. The working and protectionpaths of a new PCG circuit can be co-routed with the working andprotection paths of the primary PCG circuit, respectively.

A protection bandwidth ratio (PBR) may be calculated (block 584). ThePBR may be defined as the ratio of total bandwidth of the ACG divided bytotal available protection bandwidth (TAPB) in the PCG. The PBR may beevaluated and compared with a particular threshold.

The capacity of the protection circuit may be dynamically adjusted(block 586). The capacity of the PCG circuit may be adjusted, forexample, when the PBR falls above or below the particular threshold orthreshold range (e.g., the PBR/threshold comparison representsinsufficient protection bandwidth or the PBR/threshold comparisonrepresents inefficient protection bandwidth allocation). Changes to thePBR may be a result of, for example, changes to the required bandwidthof an ACG or the addition of a new ACG to the protection domain.

FIGS. 6A and 6B show exemplary tables that may be included in a PCGdatabase, such as PCG database 353. FIG. 6A shows an exemplary PCG Table(PCGT) 610, and FIG. 6B shows an exemplary PCG Protection Table (PPT)620. PCGT 610 may include information for the construction of protectioncircuit(s) over one or more E-NNI and/or I-NNI links. PCGT 610 mayregister all protection circuits created to support FSMPS within aP-domain and the current status of each protection circuit. PCGT 610also keeps track of available bandwidth for protection (ABP) in eachprotection circuit, total available protection bandwidth (TAPB) of thePCG, and the protection type and SRLG values of each protection circuit.PPT 620 may keep track of all active circuits that are rerouted to theprotection circuits due to faults and the current status of eachrerouted circuit. PPT may track the protection circuit number (Prot. CKTNo.) used, bandwidth (BW), type, time slots, the original active circuitgroup number (ACG ID) and the original SRLG. PPT 620 may also track thetotal restored bandwidth (Total Restored BW) of the rerouted circuits.

Each ACG may be associated with an ACG Table. FIGS. 7A and 7B showexemplary tables 710, 720 that may be included in an ACG database, suchas ACG database 354. Each ACG table is associated with a prototype path(Prtp-Path). Each ACG table 710, 720 may include information of activecircuits that are provisioned over a selected prototype path within aP-domain. Each ACG table 710, 720 includes circuit information, such asthe circuit identification (Circuit ID), bandwidth (BW), circuit type(Type), SRLG, and current status, for each circuit assigned to the ACG.An ACG may keep track of the total bandwidth requirement of allcircuits, and register the current PBR.

Generally, FSMPS circuits may be set up by the control plane through aP-domain along one of the pre-selected prototype paths (Prtp-path). Thecontrol plane might use the pre-selected Prtp-paths in a round-robinfashion to support load balancing. An entry in an associated ACG tablemay be added for each new FSMPS circuit with the new circuit'sbandwidth, type, and SRLG logged into the ACG table. In cases where thecontrol plane cannot create a FSMPS circuit along any Prtp-path, thecontrol plane may be allowed to select a path for the circuit throughthe network that is fully SRLG and node diverse from the protectioncircuits in PCG. The circuit may be called a non-conforming circuit.After the non-conforming circuit is setup, the non-conforming circuit'sSRLG values can be compared with the “Base SRLGs” of each ACG table,such as ACG tables 710, 720. When one of the non-conforming circuit'sSRLG values matches any in the “Base SRLG” of an ACG, the circuit can beadded to the corresponding ACG table. As a result, a non-conformingFSMPS circuit may be registered in multiple ACG tables, such as forexample “Ckt 3” shown in ACG tables 710 and 720.

FIG. 8 provides an exemplary flow diagram 800 of FSMPS activities when acircuit request is received at the network. A circuit request for acircuit with FSMPS may be received (block 810). When the circuit requestarrives, a Prtp-path may be selected (block 815). For example, thecontrol plane may select a Prtp-path from a pre-selected group (e.g.,the next Prtp-path in a round-robin group) to set up a sum of matchscores penalized (SMSPR) circuit. In block 820, it can be determined ifthe selected Prpt-path is successfully set up. For example, the controlplane may verify if a functional path through a P-domain has beenestablished within the parameters of the ACG. If unsuccessful, a checkmay be made for availability of other conforming circuits from thepre-selected group (block 825). If other conforming circuits areavailable, another Prtp-path may be selected (block 815). For example,the control plane may try the next Ptrp-path from the round-robin groupuntil the path is setup successfully. If no other conforming circuitsare available, a non-conforming SMSPR path may be selected (block 830).For example, when all Ptrp-paths are tried without success, the controlplane may try to setup a non-conforming SMSPR path. In block 835, it canbe determined if the selected non-conforming SMSPR is successfully setup. For example, the control plane may verify that a functional paththrough a P-domain has been established. If unsuccessful, FSMPS may berejected (block 840). If it is determined either the Prtp-path (block820) or the non-conforming SMSPR path (block 835) is successful, thecircuit may be added to the ACG. In block 845, an entry for thesuccessful path may be added to an ACG table. For example, when thecircuit is setup successfully, the control plane can add an entry to thecorresponding ACG table. In block 850, total bandwidth and PBR for theACG can be recalculated. For example, the control plane may recalculatethe total bandwidth requirement and PBR for the ACG. In block 855, thePBR of the ACG may be evaluated and compared with a particular minimumthreshold (e.g., the value “X %”). For example, the control plane maycheck if the PBR of each ACG is less than 80 percent. If all the PBRsare less than X percent, the circuit request is completed and theactivity ends (block 860). If any PBR is greater than X percent, thecontrol plane may alert a network operator to add another protectioncircuit in the PCG (block 865) before the activity ends (block 860).Logic activities for adding a new protection circuit is described inmore detail with respect to FIG. 13.

FIG. 9 provides an exemplary flow diagram 900 of FSMPS activities when anormal circuit is released from the network. The normal circuit (incontrast with, for example, a restored circuit) having FSMPS is released(block 910). For example, a customer may discontinue use of anend-to-end circuit including endpoints of the FSMPS circuit, providing asignal that the normal circuit may be released. The circuit record forthe normal circuit can be removed from all ACGs (block 920). Forexample, the control plane may search the stored ACG tables for circuitnumbers corresponding to the number of the circuit being released andremove that circuit number and corresponding information from the ACGtable. The total bandwidth and PBR in the ACG can be updated (block930). For example, if circuit “Ckt 3” shown in ACG tables 710 and 720was to be released, the control plane may remove the “Ckt 3” circuitfrom ACG tables 710 and 720 and update the Total BW and PBR in each ofACG tables 710 and 720. In block 940, a worst case PBR may berecalculated. In block 950, the worst case PBR can be compared against aparticular threshold (e.g., the value “Y %” where, for example, Y may bea value significantly smaller than the value of X in block 855 of FIG.8). In block 960, the number of protection circuits in the PCG may beevaluated. If the worst case PBR is greater than Y %, the activity iscomplete (block 970). If the ratio is not greater than Y % and there ismore than one protection circuit in the PCG, a network operator may bealerted about the possibility of removing a secondary protection circuit(block 980) before the activity ends (block 970). Thus, the bandwidth ofdedicated protection circuits may be kept to a particular capacitypercentage, allowing unneeded protection circuit capacity to bere-allocated to other circuits. Activities for removing a protectioncircuit are described in more detail with respect to FIG. 14.

FIG. 10 provides an exemplary flow diagram 1000 of FSMPS activities whena restored circuit is released from an FSMPS network. The restoredcircuit (e.g., a circuit previously restored to protection bandwidth) isreleased (block 1010). For example, a circuit may have been previouslybeen switched to a protection circuit (such as “Ckt Z” in PPT 620 ofFIG. 6B) due to a failure in the originally-dedicated active/workingcircuit. The customer may discontinue use of a restored circuit throughan FSMPS P-domain, providing a signal that the circuit may be released.The circuit record for the restored circuit can be removed from the PPT(block 1020). For example, the control plane may remove “Ckt Z” from PPT620. After the circuit record is removed, counts in the PCGT, the PPTand the ACGs can be updated. The total restored BW may be updated in thePPT (block 1030). For example, if “Ckt Z” was being removed, the controlplane may update the “Total Restored BW” in PPT 620 from “16 STS1s” to“4 STS1s.” The TAPB and the ABP may be updated in the PCGT (block 1040).For example, if “Ckt X” (with a bandwidth of 3 STS1s) was being removedfrom the PPT, the control plane may update the “TAPB” in PCGT 610 from“32 STS1s” to “35 STS1s” and the ABP for “Protection CKT A” may bechanged from “20 STS1s” to “23 STS1s.”

Still referring to FIG. 10, the PBRs in all ACGs may also be updated asfollows. In block 1050, the worst case PBR may be recalculated. In block1060, the worst case PBR can be compared against a particular threshold(e.g., the value “Y %” where, for example, Y may be a valuesignificantly smaller than the value of X in block 855 of FIG. 8). Inblock 1070, the number of protection circuits in the PCG may beevaluated. If the worst case PBR is greater than Y %, the activity iscomplete (block 1080). If the ratio is not greater than Y % and there ismore than one protection circuit in the PCG, a network operator may bealerted about the possibility of removing a secondary protection circuit(block 1090), so that unneeded protection circuit capacity can bere-allocated to other circuits. After the network operator is alertedthe activity may end (block 1080).

FIG. 11 provides an exemplary flow diagram 1100 of FSMPS activities whena network failure occurs that affects some circuits in ACGs. The failureof one or more circuit in an ACG may occur (block 1110). For example, afailure may occur in a link affecting “Ckt 1” and “Ckt 2” in ACG tables710 of FIG. 7A. When a failure occurs, the two ends of the circuit cancoordinate with each other to re-route the affected ACG circuits over toPCG protection circuits one-by-one (block 1120). For example, failed“Ckt 1” may be re-routed over PCG protection circuit “Ckt X” shown inPPT 620 of FIG. 6B and failed “Ckt 2” may be re-routed over PCGprotection circuit “Ckt Y” also shown in PPT 620. For each re-routedcircuit, updates may be made to the ACG table(s), PCGT, and PPT. Thecircuit record may be removed from its respective ACG table (block1130). For example, the entries for “Ckt 1” and “Ckt 2” may be removedfrom ACG table 710. An entry may be created in the PPT to record the newcircuit identification, original ACG ID, and the time slots of therestored circuit (block 1140). For example, “Ckt X” in PPT table 620 mayinclude a reference to Original ACG ID “1,” time slots “1-3,” andOriginal SRLG “2, 23, 45, 64.” The PCG table and ACG table(s) may alsobe updated by recalculating the ABP & TAPB in the PCG and totalbandwidth & PBR for the affected ACGs (block 1150). A check may be madefor another ACG circuit to re-route (block 1160). If there is anothercircuit to re-route then the course of action may be repeated beginningat block 1120. If there is not another ACG circuit to re-route, then thePBR of each ACG may be updated (block 1170). In block 1180, the PBR ofeach ACG may be evaluated and compared with a particular minimumthreshold (e.g., the value “X %”). If any ACG has a PBR that is greaterthan or equal to X percent, a network operator may be alerted to add aprotection circuit in the PCG (block 1185). Once the network operator isalerted, or if the PBR of each ACG is less than X percent in block 1180,then the activity ends (block 1190).

FIG. 12 provides an exemplary flow diagram 1200 of FSMPS activities whena network failure is fixed. The fault in one or more circuits in an ACGmay be repaired (block 1210). For example, a circuit may have beenpreviously been switched to a protection circuit (such as “Ckt X” in PPT620 of FIG. 6B) due to a failure in the originally-dedicatedactive/working circuit (such as “Ckt 1” in ACG table 710). Once thefailure in the originally-dedicated active/working circuit has beenrepaired and the circuit is rolled back to the original active/workingcircuit, the restored circuit may be released. When a network fault isfixed, SMSPR circuits affected by the fault can be either reverted backto their original circuit (if the circuit is not torn-down) or rolledback to a new circuit created along the Prtp-path of the original ACG(block 1220). For example, PCG protection circuit “Ckt X” shown in PPT620 of FIG. 6B may be re-routed back to “Ckt 1” (in ACG table 710) whenthe original active/working circuit is repaired. For each reverted orrolled-back SMSPR circuit, updates may be made to the affected ACGtable(s), PCGT, and PPT. The circuit record for the SMSPR circuit in thePPT may be removed (block 1230). For example, the circuit record for“Ckt X” in PPT 620 may be removed. The TAPB and ABP in the PCGT can thenbe updated (block 1240). For example, if “Ckt X” (with a bandwidth of 3STS1s) was being removed from the PPT, the control plane may update the“TAPB” in PCGT 610 from “32 STS1s” to “35 STS1s” and the ABP for“Protection CKT A” may be changed from “20 STS1s” to “23 STS1s.” Thecircuit may then be added back to its original ACGs with the requiredcircuit information and total bandwidth & PBRs of affected ACGs updated(block 1250). A check for more repaired circuits may be made (block1255). If there is another circuit to revert or roll back, then thecourse of action may be repeated beginning at block 1220. After allaffected circuits are reverted or rolled back, the worst case PBR may berecalculated. The worst case PBR can be compared against a particular Y% threshold (block 1260). In block 1270, the number of protectioncircuits in the PCG may be evaluated. If the worst case PBR is greaterthan Y %, the activity is complete (block 1280). If the ratio is notgreater than Y % and there is more than one protection circuit in thePCG, a network operator may be alerted about the possibility of removinga secondary protection circuit (block 1290).

FIG. 13 provides an exemplary flow diagram 1300 of FSMPS activities whena network operator decides to add a new protection circuit in the PCG. Adecision is made to add a new protection circuit in the PCG (block1310). The decision may include identifying the desired bandwidth anddetermining that the new circuit be of the same protection type (e.g.,1+1 or unprotected) as existing circuits in the PCG. The new protectioncircuit may be co-routed with the primary protection circuit. The newprotection circuit may be added to PCGT (block 1320). The total BW-P,ABP, and TAPB counts in the PCGT may be updated (block 1330). The PBRsin all ACGs can be updated (1340).

FIG. 14 provides an exemplary flow diagram 1400 of FSMPS activities whena network operator decides to remove one protection circuit in a PCG. Adecision may be made to remove one protection circuit in a PCG (block1410). For example, the network operator may choose to remove anunnecessary protection circuit to allow that circuit capacity to be usedelsewhere. All secondary protection circuits can be scanned to identifythe protection circuit that carries the minimal number or bandwidth ofrestored circuits (block 1420). The protection circuit that carries theminimal number or bandwidth of restored circuits may be designated as“TBR” (to be removed). Each SMSPR circuit on the TBR may be re-routed(block 1430). The re-routing of each circuit may be accomplished by (1)creating a new SMSPR circuit with the same attributes in anotherprotection circuit; (2) coordinating between end points using signalingto roll over the SMSPR circuit to the new circuit; (3) updating the ABPof the affected protection circuit in the PCGT; and (4) revising circuitinformation of the re-routed circuit in the PPT. After all the circuitson TBR are migrated to other protection circuits, the TBR may be torndown, its entry removed from the PCGT, and the TAPB updated for the PCGT(block 1440). If any migration fails, the TBR protection circuit may notbe removed. If the migrations are successful, the PBRs in all the ACGsmay be updated (block 1450).

FIG. 15 provides an exemplary flow diagram 1500 of certain FSMPSactivities when a protection circuit fails. When a protection circuitfails, there may be many possible scenarios depending on the protectionand restoration (P&R) types implemented for the protection circuits. Inflow diagram 1500, exemplary actions for two P&R types are provided. Inone P&R type, the circuit is unprotected, and in another P&R, type thecircuit is 1+1 protected. A protection circuit fails (block 1510), andthe P&R type of the protection circuit may be identified (block 1515).In FIG. 15, only two P&R types are provided. However other P&R types maybe used.

If the protection circuit is identified as “Unprotected,” SMSPRprotection may be lost on the failed protection circuit. Note that otherprotection circuits in the PCG may not fail. All client SMSPR circuitsrestored to the failed PCG circuit may be interrupted until theprotection circuit can be repaired and put back in service. In block1520, the failed protection circuit may be flagged as “Being Repaired”in the PCGT and the TAPB updated in the PCGT. In block 1525, theaffected client circuits previously restored to the failed circuit maybe flagged as “Out-of-Service” in the PPT. In block 1530, the PBRs forall ACGs may be re-calculated. In block 1535, the PBR of the ACG may beevaluated and compared with a particular minimum threshold (e.g., thevalue “X %”). If the PBR is not less than X percent, a network operatormay be alerted to add a protection circuit in the PCG (block 1540). Inblock 1545, the failed protection circuit may be repaired. In block1550, all interrupted client circuits may be restored by unmarking theclient circuits in the PPT and the protection circuits in PCGT. In block1555, the TAPB may be updated in the PCGT. In block, 1560, the PBRs forall ACGs can be re-calculated.

If the protection circuit is identified as “1+1 protected,” protectionswitching can take place so that all client restored circuits areprotected in the event of the protection circuit failure. There may beno change to the TAPB count in the PCGT. In block 1570, the protectioncircuit in the PCGT can be marked as “Degraded.” In block 1575, thefailed protection circuit—that is the previously active protectioncircuit—may be repaired. Once the failed protection circuit is repaired,the 1+1 protection may be re-activated for the protection circuit (block1580). The “degraded” flag in the PCGT may then be removed (block 1585).

The service actions described herein with respect FIGS. 8-15 mayillustrate different situations in a service provider's FSMPS service.Other situations may occur and can be treated as exceptions according tothe general principles described herein.

Circuit and restoration related activities (e.g., “set up,” “tear-down,”“release,” “restore,” “protection switching,” “end-point coordination,”etc.) discussed in FIGS. 8-15 above may be carried out according to IOTNcontrol plane signaling and routing procedures as specified byinternational standards bodies, such as the Internet Engineering TaskForce (IETF) Generalized Multi-Protocol Label Switching (GMPLS) Requestfor Comments (RFCs)—particularly RFCs 4426, 4872 and 4873—and OpticalInternetworking Forum (OIF) signaling and routing implementationagreements (IAs).

Referring now to FIG. 16, international standards, such as OIF UNI andE-NNI signaling standards, define a service level (SL) parameter to beused by a client device over UNI or E-NNIs to inform the source node oran ingress node of a P-domain what P&R feature should be used toprovision the circuit within the P-domain. The SL parameter can becarried in path setup signaling messages between domains, so eachdown-stream domain will know what P&R scheme should be provisioned. Forthe case of FSMPS, the SL parameter may be assigned to an 8-bit integerof which all border nodes in all P-domains are made aware. FIG. 16 showsan example of how the SL parameter can be used to instruct all P-domainsin a network to trigger the FSMPS mechanism within their respectiveP-domain. Specifically, NMS/OSS 130 may provide an SL parameter(“SL=FSMPS”) to source node 1610 in P-domain A. A path setup signalingmessage including the parameter SL=FSMPS may be passed from border node1620 to ingress node 1630 and from border node 1640 to ingress node 1650to inform each domain what P&R feature should be used to provision acircuit within the respective P-domains.

FIG. 17 provides an example of an implementation of FSMPS. A serviceprovider may decide to offer FSMPS between two major metro markets. Theservice provider may identify one point-of-presence in each market, suchas an A-end 1710 in Market “A” and a Z-end 1720 in Market “Z.” Based ona service forecast, the provider may pre-provision the first (primary)protection circuit 1730 between A and Z of certain bandwidth withdesired protection type and may pre-select a set of prototype paths1740, 1750, 1760 which are mutually disjoint at link and node levels.Furthermore, the selected prototype paths are also disjoint from theprimary protection circuit 1730. Customers for the FSMPS may be allowedto order a range of circuit types. As an example, for SONET service, thecircuit can be STS1, STS3c, STS12c, STS48c, etc.

For each customer order, the control plane may route the circuit usingone of the pre-selected routes 1740, 1750, 1760. When the worst caseprotection bandwidth (WCPB) is exceeding X % of the primary protectioncircuit bandwidth, one secondary protection circuit 1770 will be addeddynamically to the protection circuit group. When network faults occur,all affected customer FSMP circuits through any of routes 1740, 1750,1760 will be restored using one or more of protection circuits 1730and/or 1770. In one implementation, restoration after the first failuremay be guaranteed. The number of restorations guaranteed for subsequentfailures may be dependent upon the protection type provisioned for theprotection circuits. When services are terminated and circuits arereleased, the WCPB can be recalculated. If the recalculated WCPB is lessthan Y % of total available protection bandwidth, one protection circuit1730, 1770 can be released. Thus, the FSMPS can allow the number ofcustomer circuits to grow in real-time and can dynamically adjustprotection circuit capacity to meet customer traffic profile.

Implementations described herein may provide a flexible shared meshprotection service (FSMPS) for intelligent optical transport networks(IOTNs). In one exemplary embodiment, provided herein are a class ofshared mesh protection service for TDM-based OTNs (e.g., SONET/SDH,G.709 OTN), an underlying networking mechanism required to support theservice, and service actions to guide implementation of the service. TheFSMPS may allow multiple client circuits between a source and adestination to share protection bandwidth, which can reduce bandwidthrequirements for service protection.

Compared to traditional shared mesh protection schemes, the FSMPSprovides greater flexibility in a number of ways. One way, for example,is that FSMPS may remove the restriction that client circuits (i.e.,circuits subject to protection) and the shared protection circuit(s) beof the same circuit type. Another way is that the size of a servicegroup in FSMPS can be adjusted dynamically, contrary to thestatically-provisioned, fixed-size service group in traditional sharedmesh applications. Using FSMPS, the number of client circuits and sharedprotection circuits can grow or reduce depending on the demands. FSMPSmay also provide additional protection to the shared protection circuitsto ensure client circuits can withstand multiple faults in sequence.Implementation and deployment of FSMPS can be segmented by control planerouting or vendor domain boundaries, allowing domains to implement theservice in different ways. Also, FSMPS can be implemented to provideshared mesh protection on both path (intra-domain) and link(inter-domain) levels.

The foregoing description provides illustration and description, but isnot intended to be exhaustive or to limit the embodiments to the preciseform disclosed. Modifications and variations are possible in light ofthe above teachings or may be acquired from practice of systems andmethods disclosed herein.

For example, while series of blocks have been described with regard tothe flowcharts of FIGS. 5C and 8-15, the order of the blocks may differin other implementations. Further, non-dependent acts may be performedin parallel.

Implementations described herein may be implemented in methods and/orcomputer program products. Accordingly, implementations may be embodiedin hardware and/or in software (including firmware, resident software,micro-code, etc.). Furthermore, implementations described herein maytake the form of a computer program product on a computer-usable orcomputer-readable storage medium having computer-usable orcomputer-readable program code embodied in the medium for use by or inconnection with an instruction execution system. The actual softwarecode or specialized control hardware used to implement the systems andmethods described herein is not limiting. Thus, the operation andbehavior of the implementations were described without reference to thespecific software code—it being understood that software and controlhardware could be designed to achieve implementations based on thedescription herein.

Further, certain implementations described herein may be implemented as“logic” that performs one or more functions. This logic may includehardware, such as a processor, microprocessor, an application specificintegrated circuit or a field programmable gate array; or a combinationof hardware and software.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps, or components, but does not preclude thepresence or addition of one or more other features, integers, steps,components, or groups thereof.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the invention. In fact, many of these features may becombined in ways not specifically recited in the claims and/or disclosedin the specification.

No element, act, or instruction used in the description of the presentapplication should be construed as critical or essential to theinvention unless explicitly described as such. Also, as used herein, thearticle “a” is intended to include one or more items. Where only oneitem is intended, the term “one” or similar language is used. Further,the phrase “based on,” as used herein is intended to mean “based, atleast in part, on” unless explicitly stated otherwise.

What is claimed is:
 1. A system comprising: one or more active/workingcircuit groups to transfer information through a protection domain, theprotection domain defined by a plurality of network devices and aplurality of links connecting the plurality of network devices between astart point and an end point; a primary protection circuit through theprotection domain, the primary protection circuit being disjoint fromthe one or more active/working circuit groups and providing sharedprotection for the one or more active/working circuit groups, theprimary protection circuit being comprised of an individual protectioncircuit, a capacity of the primary protection circuit being dynamicallyadjusted when a protection bandwidth ratio is outside a predeterminedthreshold, and the protection bandwidth ratio being based on a totalbandwidth of the one or more active/working circuit groups divided by atotal available protection bandwidth of the primary protection circuit;a secondary protection circuit, the secondary protection circuitproviding shared protection for the one or more active/working circuitgroups, and the secondary protection circuit being used to restore oneor more faults when a worst case protection bandwidth exceeds aparticular threshold associated with the capacity of the primaryprotection circuit; and a processor to: receive a request to remove oneof the primary protection circuit or the secondary protection circuit;designate one of the primary protection circuit or the secondaryprotection circuit for removal based on a comparison of respectivebandwidths of the primary protection circuit and the secondaryprotection circuit; re-route each path associated with the designatedone of the primary protection circuit or the secondary protectioncircuit, the processor, when re-routing each path, being to one of:re-route each path to the one of primary protection circuit or thesecondary protection circuit that is not designated for removal, orre-route each path to another secondary protection circuit,  the othersecondary protection circuit being different than the secondaryprotection circuit; and update the protection bandwidth ratio for eachof the one or more active/working circuit groups.
 2. The system of claim1, where the plurality of links supports at least one of: anexternal-network network interface (E-NNI); or an internal-networknetwork interface (I-NNI).
 3. The system of claim 1, where the secondaryprotection circuit is disjoint from the primary protection circuit. 4.The system of claim 1, where each of the one or more active/workingcircuit groups comprises a fully disjoint prototype path.
 5. The systemof claim 1, further comprising: a storage device to store a protectioncircuit group table with a registration of at least one of the primaryprotection circuit or the secondary protection circuit and a currentstatus of at least one of the primary protection circuit or thesecondary protection circuit.
 6. The system of claim 5, where thestorage device is further to store one or more of: an availablebandwidth for protection in the primary protection circuit, a totalavailable protection bandwidth of the primary protection circuit, or aprotection type of the primary protection circuit.
 7. The system ofclaim 1, further comprising: a storage device to store an active/workingcircuit group table with a registration of each of the one or moreactive/working circuit groups and a current status of each of the one ormore active/working circuit groups.
 8. The system of claim 1, where eachactive/working circuit group comprises one or more individual circuitsegments, and an information stream from the one or more individualcircuit segments of the one or more active/working circuit groups isautomatically switched to at least one of the primary protection circuitor the secondary protection circuit in the event of a failure of the oneor more individual circuit segments.
 9. The system of claim 1, where atleast two of the one or more active/working circuit groups, the primaryprotection circuit, or the secondary protection circuit are of differentcircuit types.
 10. A method comprising: selecting, by one or moredevices, one or more prototype paths over a protection domain within anoptical transport network, the prototype paths defining anactive/working circuit group; configuring, by the one or more devices, aprimary protection circuit over the protection domain to provide sharedprotection for the active/working circuit group, the primary protectioncircuit being disjoint from the active/working circuit group;calculating, by the one or more devices, a protection bandwidth ratiobased on a total available protection bandwidth of the primaryprotection circuit and a total bandwidth of the active/working circuitgroup; dynamically adjusting, by the one or more devices, a capacity ofthe primary protection circuit when the protection bandwidth ratio isoutside a predetermined threshold; determining, by the one or moredevices, whether the dynamically adjusted capacity of the primaryprotection circuit satisfies a worst case protection bandwidththreshold; adding, by the one or more devices and when the dynamicallyadjusted capacity of the primary protection circuit does not satisfy aworst case protection bandwidth threshold, a secondary protectioncircuit, the secondary protection circuit being to provide sharedprotection for the active/working circuit group; receiving a request toremove one of the primary protection circuit or the secondary protectioncircuit; designating one of the primary protection circuit or thesecondary protection circuit for removal based on a comparison ofrespective bandwidths of the primary protection circuit and thesecondary protection circuit; re-routing each path associated with thedesignated one of the primary protection circuit or the secondaryprotection circuit, the re-routing each path including one of:re-routing each path to the one of primary protection circuit or thesecondary protection circuit that is not designated for removal, orre-routing each path to another secondary protection circuit, the othersecondary protection circuit being different than the secondaryprotection circuit; and updating the protection bandwidth ratio for eachof the one or more active/working circuit groups.
 11. The method ofclaim 10, further comprising: automatically switching an informationstream from an individual circuit segment of the active/working circuitgroup to at least one of the primary protection circuit or the secondaryprotection circuit when a failure of the individual circuit segment isdetected.
 12. The method of claim 10, where the active/working circuitgroup and the protection circuit are of different types.
 13. The methodof claim 10, where an amount of prototype paths in the active/workingcircuit group is adjusted dynamically.
 14. The method of claim 10, wherethe secondary protection circuit is disjoint from the primary protectioncircuit.
 15. The method of claim 10, where the protection domainincludes an internal-network network interface (I-NNI) domain or anexternal-network network interface (E-NNI) domain.
 16. The method ofclaim 10, where the protection domain includes at least oneinternal-network network interface (I-NNI) domain and at least oneexternal-network network interface (E-NNI) domain.
 17. The method ofclaim 10, further comprising: creating an active/working circuit grouptable for each prototype path.
 18. A system comprising: a plurality ofcircuits; a primary protection circuit; a secondary protection circuit;and a transport network, including a shared protection mechanism, that:allows a quantity of circuits, of the plurality of circuits, between aparticular start point and particular end point to increase inreal-time, dynamically adjusts a capacity of the primary protectioncircuit when a protection bandwidth ratio is outside a predeterminedthreshold, the protection bandwidth ratio being based on a totalbandwidth of the number of circuits divided by a total availableprotection bandwidth of the primary protection circuit, determineswhether the dynamically adjusted capacity of the primary protectioncircuit satisfies a worst case protection bandwidth threshold; adds,when the dynamically adjusted capacity of the primary protection circuitdoes not satisfy a worst case protection bandwidth threshold, thesecondary protection circuit, the secondary protection circuit being toprovide shared protection for the active/working circuit group; receivesa request to remove one of the primary protection circuit or thesecondary protection circuit; designates one of the primary protectioncircuit or the secondary protection circuit for removal based on acomparison of respective bandwidths of the primary protection circuitand the secondary protection circuit; re-routes each path associatedwith the designated one of the primary protection circuit or thesecondary protection circuit, the re-routing each path including to oneof: re-routing each path to the one of primary protection circuit or thesecondary protection circuit that is not designated for removal, orre-routing each path to another secondary protection circuit,  the othersecondary protection circuit being different than the secondaryprotection circuit; and updates the protection bandwidth ratio for eachof the one or more active/working circuit groups.
 19. The system ofclaim 18, where the transport network automatically switches aninformation stream to at least one of the primary protection circuit orthe secondary protection circuit in the event of a failure of a circuit.20. A system comprising: one or more devices to: select one or moreprototype paths over a protection domain within an optical transportnetwork, the one or more prototype paths defining an active/workingcircuit group; select a primary protection circuit over the protectiondomain to provide shared protection for the active/working circuitgroup, the protection circuit being disjoint from the active/workingcircuit group; dynamically adjust a capacity of the primary protectioncircuit when a protection bandwidth ratio is outside a predeterminedthreshold, the protection bandwidth ratio being based on a totalbandwidth of the active/working circuit group divided by a totalavailable protection bandwidth of the primary protection circuit;determine whether the dynamically adjusted capacity of the primaryprotection circuit satisfies a worst case protection bandwidththreshold; add, when the dynamically adjusted capacity of the primaryprotection circuit does not satisfy a worst case protection bandwidththreshold, the secondary protection circuit, the secondary protectioncircuit being to provide shared protection for the active/workingcircuit group; receive a request to remove one of the primary protectioncircuit or the secondary protection circuit; designate one of theprimary protection circuit or the secondary protection circuit forremoval based on a comparison of respective bandwidths of the primaryprotection circuit and the secondary protection circuit; re-route eachpath associated with the designated one of the primary protectioncircuit or the secondary protection circuit, the one or more devices,when re-routing each path, being to one of: re-route each path to theone of primary protection circuit or the secondary protection circuitthat is not designated for removal, or re-route each path to anothersecondary protection circuit,  the other secondary protection circuitbeing different than the secondary protection circuit; and update theprotection bandwidth ratio for each of the one or more active/workingcircuit groups.